Many manually adjustable prior art vehicle seats have incrementally adjustable vehicle seat track members on which the entire seat assembly slides between a plurality of discrete fore and aft positions, wherein two track members are locked in place with respect to each other by a separate external locking means having teeth that protrude into aligned apertures in one or both of the two track members. There are, however, numerous problems associated with incrementally adjustable vehicle seat tracks and the locking mechanisms therefor, not the least of which is partial locking. Partial locking occurs when the teeth of the external locking means do not fully engage the apertures in the tracks on one or both of the inboard and outboard seat tracks. This problem is particularly acute in modern vehicle seating installations which utilize an integrated restraint system ("I.R.S."), where at least one anchor point for the passenger seat belts is attached to the seat assembly for adjustably sliding movement with the vehicle seat. I.R.S. arrangements typically require that both of the inboard and outboard seat tracks to be simultaneously fully locked under crash-like conditions, so as to safely handle the increased loading applied to the seat tracks by the seat belt attachments.
To ensure such simultaneous full locking, manually actuated, infinitely adjustable seat track locking mechanisms have recently found favour. These devices have no discrete teeth or detent members which engage slots in the seat track slides etc. Rather, infinitely adjustable seat track locking mechanisms typically use spring clutches or other devices to lock at any position upon release of the actuation mechanism by the user. Infinitely adjustable seat track locking mechanisms have found such favour despite their increased cost and complexity because they substantially solve the problem of partial locking discussed above, and offer more adjustment possibilities to the seat track designer, and ultimately the seat occupant. Also, generally speaking, infinitely adjustable seat track locking mechanisms are capable of providing for higher loading before failure under crash-like deceleration conditions, and substantially free up the interior space of the vehicle seat track slide to allow use of this space for other purposes (such as rollers or anti-rattle mechanisms).
One example of a recent infinitely adjustable locking mechanism is disclosed in U.S. Pat. No. 5,183,236 (Droulon), which patent is to a locking mechanism for rectilinear or circular displacement mechanical jacks. A mechanical jack is a broad term used in the Droulon patent to refer to a type of mechanism that has two co-operating members that are movable one with respect to the other, and that permits selective locking of the two members in chosen displacement one to the other.
In one embodiment of the Droulon patent, a casing is slidably mounted on a jack rod, which jack rod is part of the vehicle seat, for relative sliding movement of the casing along the jack rod. The casing is also operatively mounted in secure relation to the vehicle. A "V"-shaped pawl block is retained within the casing for movement between a locking position and an unlocking position, as will be described subsequently. The pawl block has a pair of inclined ramp surfaces that define a "V"-shaped cavity, which "V"-shaped cavity, together with an engagement surface on the rod, define a substantially triangular recess. A striated roller member is rotatedly mounted within the triangular recess for rolling contact with the engagement surface on the rod.
The Droulon pawl block has first and second sloped side surfaces that converge and join at a flat end surface. The first sloped side surface abuts against a co-operating corresponding sloped abutment surface on the casing. The second sloped side surface is in intimate supported contact with a rotatable generally round cam member, which rotatable cam member is also retained within the casing for movement between a blocking position and releasing position. In the blocking position, the cam member retains the pawl block in its locking position, and in the releasing position, the cam member retains the pawl block in its unlocking position. In either the locking or unlocking position of the pawl block, the pawl block is angularly pinched in unstable rockable relation between the generally round cam member and the sloped abutment surface of the casing.
The Droulon infinitely adjustable locking mechanism works in the following manner. In its locking position, the pawl block is wedged between the cam member and the sloped abutment surface of the casing, and is forced into its locking position whereat the striated roller is forced into intimate engagement with the engagement surface on the rod. The striated roller is trapped in centred relation within the triangular recessed defined by the engagement surface and the pawl block. When an accelerative or decelerative force is applied to the vehicle seat, the striated roller attempts to roll along the engagement surface of the rod; however, the striated roller becomes pinched between the rod and the respective inclined ramp surface of the pawl block. Accordingly, the striated roller cannot move along the rod, and thus the casing and the rod are locked with respect to each other.
In its unlocking position, the Droulon cam member is rotated so that the pawl block is not pushed into its locked position. A spring member biases the pawl block to its unlocking position, whereat the striated roller does not contact, or at least loosely contacts, the engagement surface on the rod. The casing and the rod may then be moved relative to one another. Once in a desired position, the cam member is returned to its blocking position at the pawl block is forced to its locking position, whereat the striated roller is again brought into locking engagement with the engagement surface of the rod, thus locking the casing and the rod with respect to each other.
While the Droulon device makes a definite improvement in the art, it has been found that the generally round cam member tends to act as a pivot point for the pawl block. Accordingly, there tends to be relative movement, and therefore looseness, between the pawl block and the sloped side surface, and also between the pawl block and the striated roller. This looseness between adjacent parts is known in the art as "chuck". The problem of chuck arises inherently in any mechanical vehicle seat locking device, and is the result of the clearances that are necessarily a part of any device containing mass-produced parts adapted to undergo relative movement. Chuck is a highly undesirable characteristic in automobile seat back hinges, for both safety and aesthetic reasons.
The Droulon mechanism exhibits a higher degree of chuck than is ideally desirable because a generally round cam member is used to control the positioning of the pawl block, which cam acts as a pivot point for the pawl block. This imparts a first source of chuck into the Droulon device. It can be seen that there is a second source of chuck imparted to the Droulon device on account of the clearances between the first sloped side surface of the pawl block and the co-operating, correspondingly sloped, abutment surface of the casing. There is a third source of chuck in relation to lost motion between the striated roller and the remaining components of the device. These three sources of chuck are highly undesirable, as they stack together to cause an overall looseness in the operation of the locking mechanism.
Another factor that affects the proper operation of the Droulon prior art locking mechanism is that it requires close manufacturing tolerances of the various parts that make up the locking mechanism. That is, if the parts have been manufactured slightly undersized, the striated roller may not properly engage the engaging surface on the rod, and resultingly, the locking mechanism may not lock the two co-operating elements with respect to each other. Conversely, if the parts have been manufactured slightly oversized, the locking mechanism may jam. The need for close manufacturing tolerances increases the cost and complexity of manufacture.
Another problem associated with the Droulon type of infinitely adjustable locking mechanism is the tendency of the various parts, such as the cam member, to physically wear after a period of time. Such wear causes increased looseness in the mechanism and accordingly, an even greater amount of chuck. In extreme circumstances, a significant amount of wear of the various parts could mean that the striated roller does not properly engage the engaging surface on the rod, thus perhaps precluding the locking mechanism from locking the two cooperating elements with respect to each other.
Another inherent problem with the Droulon mechanism is that it tends to lock better in one direction than in the other opposite direction. This directionality problem is overcome in the several illustrated embodiments by the inclusion of two "V"-shaped pawl blocks, each pawl block retaining a separate striated roller, and each pawl block abutting against opposed sloped sides of the casing. This solution introduces problems of increased degrees of chuck, increased overall size of the locking mechanism, increased complexity of manufacturing, and increased cost.
It is an object of the present invention to provide a mechanism for selectively locking in infinitely adjustable relation to each other, a stationary element and a co-operating movable element, wherein chuck is minimized.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other, a stationary element and a co-operating movable element, wherein relatively large tolerances in the size of the parts of the mechanism are within acceptable safety limits.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other a stationary element and a co-operating movable element, wherein wear of the parts of the mechanism is automatically accommodated.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other a stationary element and a co-operating movable element, which mechanism is relatively simple to manufacture.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other a stationary element and a co-operating movable element, which mechanism is relatively inexpensive to manufacture.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other a stationary element and a co-operating movable element, which mechanism is relatively small in size.
It is an object of the present invention to provide a mechanism for selectively locking an infinitely adjustable relation to each other a stationary element and a co-operating movable element, wherein the mechanism employs a single roller and locks equally well in opposite linear directions.